The invention relates to a catalytic burner for or on a combuster of, in particular, a power station installation, having the features of the preamble of claim 1.
Such a catalytic burner, which is arranged on a combuster of a gas turbine, is known from JP 61-276 627. The burner has a central, secondary injection device for the direct injection of a fuel into the combuster. The secondary injection device is enclosed by an inner annular duct, which leads to the combuster and in which is arranged a swirler. This swirler surrounds the secondary injection device as an annulus. In addition, an outer annular duct is arranged in the combuster and this likewise leads to the combuster and surrounds, in the form of an annulus, the inner annular duct and, therefore, the secondary injection device. A catalyzer, which surrounds the inner annular duct and therefore also the secondary injection device, is arranged in the outer annular duct. A primary injection device is, furthermore, arranged upstream of the catalyzer in the outer annular duct, and this primary injection device is used for injecting a fuel into the outer annular duct. The known burner is, furthermore, equipped with radially arranged catalyzers and radially arranged injection devices, by means of which a radial flow into the combuster can be realized.
The present invention concerns the problem of providing, for a burner of the type mentioned at the beginning, an improved embodiment which, in particular, increases the stability of the combustion in the combuster.
This problem is solved by means of the subject matter of the independent claim. Advantageous embodiments are the subject matter of the dependent claims.
The invention is based on the general idea of configuring the burner in such a way that the flow through the catalyzer has swirl, at least at its entry into the combuster. Subjecting the flow emerging from the catalyzer to a swirl permits support for the formation of a central recirculation zone in the combuster. This recirculation zone leads to the flame front in the combuster being anchored and, therefore, to a stabilization of the combustion process.
A particularly advantageous development is one in which the dimensions of the annular duct and the combuster are matched to one another in such a way that a cross-sectional expansion is configured at the transition from the annular duct to the combuster. By means of this measure, the swirl flow can more or less collapse on entry into the combuster, by which means an additional stabilization is provided for the central recirculation zone.
In this arrangement, a swirl generation device arranged in the annular duct can be expediently positioned directly at the transition between annular duct and combuster. This measure permits the swirl flow to enter the combuster directly after its generation, thus reducing friction losses.
According to an advantageous embodiment, the secondary injection device can be configured for injecting a liquid fuel and for injecting a gaseous fuel, so that the secondary injection device can inject the liquid fuel into the combuster independently of the gaseous fuel. This construction makes it possible to inject gaseous and/or liquid fuel directly into the combuster to suit the requirements under transient operating conditions of the burner, for example in order to achieve a desired temperature in the combuster even when the catalyzer has not yet reached its operating temperature, in particular when running up the burner.
A further special feature may be seen in the fact that a flow path for an oxidant or an oxidant mixture, in particular air and/or the fuel-oxidant mixture, is guided through the burner in such a way that, essentially, the oxidant or the oxidant mixture reaches the combuster through the annular duct only. In this embodiment, the primary injection device and the secondary injection device are arranged in series with respect to this flow path and, therefore, with respect to the oxidant supply. By this means, the oxidant is first available for the catalytic combustion and only subsequentlyxe2x80x94where presentxe2x80x94in the combuster for the reaction with the directly injected fuel. This means that a purely catalyzer burner operation with a relatively high volume flow, in which all the oxidant supplied, usually oxygen, flows through the catalyzer, can be obtained.
Furthermore, an additional reaction zone can be additionally configured in the annular duct upstream of the primary injection device, with which is associated an additional injection device for injecting a fuel or a fuel-oxidant mixture into the additional reaction zone. Such an additional reaction zone permits the achievement of a rapid increase in the temperature of the catalyzerxe2x80x94for starting the burner, for examplexe2x80x94so that the catalyzer rapidly achieves its operating temperature.
The use of a suitable control system permits the burner to be switched over, as a function of predetermined parameters, between, for example, a pilot operation, in which the secondary injection device is activated and the primary injection device is deactivated, a catalyzer operation, in which the primary injection device is activated and the secondary injection device is deactivated, and a mixed operation, in which the primary injection device and the secondary injection device are more or less active. By means of the various modes of operation, the burner can be optimally adapted to changing boundary conditions. As an example, the burner can be adapted in this way to a current power demand placed on the burner and/or to requirements with respect to flame stability and pollutant emission and/or to the current temperature of the catalyzer.
Further important features and advantages of the invention are provided by the subclaims, from the drawings and from the associated description of the figures, using the drawings.